Sounds of Science – March 6, 2017

Orbital debris and the growing junkyard around Earth

Reference story: “Earth’s orbiting junkyard threatens the space economy: ‘It’s kind of like the Wild West’”

The basic challenge is simple but severe: Earth orbit is filling with debris moving at enormous speeds. Images of Earth from orbit do not show a visible cloud of junk, but that does not mean the problem is small. Even relatively tiny fragments can carry enough energy to cripple a spacecraft. As launches become cheaper and more commercial actors put up large constellations of satellites, the long-term sustainability of low Earth orbit becomes a serious scientific and policy question.

Suggested questions and responses

1) Images of the Earth taken from orbit don’t show a cloud of material. How bad are things right now?

NASA and other agencies consistently track hundreds of thousands of pieces of orbital debris. They do not have to be large either: even something about the size of a dime can do a great deal of damage if it hits a spacecraft at orbital speed. The core issue is that objects in different orbital planes can cross each other at astonishing relative velocities, on the order of tens of thousands of kilometres per hour. People may know that the International Space Station is occasionally maneuvered to avoid debris, but other satellites also need their own course corrections. At the moment we are tracking enough material that the system is still manageable, but only just.

2) We’re hearing about the commercialization of space, and launches of hundreds of satellites at a time. Could this actually be self-limiting in the long term?

One of the most interesting things about commercial space is that it pushes toward smaller and cheaper spacecraft. Micro- and nano-satellites are attractive because instead of costing hundreds of millions of dollars, systems can sometimes be built for only a few million. But if many companies want global coverage, that naturally leads to very large constellations. One launch of a hundred satellites sounds dramatic enough; repeat that often enough and suddenly you are talking about many thousands of new objects in orbit. At that point the environment can become much more hazardous.

3) NASA scientists predicted that low Earth orbit could become inaccessible if there were a cascade of debris — the Kessler Syndrome. How likely is this?

Kessler Syndrome is mathematically well founded. If enough material accumulates in orbit, one major collision can produce thousands of new fragments, and those fragments can then trigger further collisions. It becomes a chain reaction. If that process runs away badly enough, then low Earth orbit can become a region where the probability of collision is so high that putting new material there becomes extremely difficult.

Tracking, cleanup, and the future of orbital regulation

4) Is there anything that can be done, other than not launching more satellites?

Removing debris is very hard because the material is moving so quickly. In principle, though, what we really want is to deorbit it: slow it down enough that it drops into the atmosphere, or else capture it and bring it down more deliberately. Proposed methods have included nets, harpoons, solar sails, and even the idea of putting large puffs of atmosphere into orbital regions to create drag without creating more debris. Japan also experimented with an electromagnetic tether intended to attract and slow material, although that particular attempt failed to deploy properly.

5) So for the moment it sounds like we need to track things better?

Yes, and it is interesting that debris tracking itself is becoming potentially commercially viable. A company like LeoLabs was already offering independent tracking information for debris larger than about an inch. When you remember that there are tens of billions of dollars of hardware already in orbit, it becomes very clear why there is a market for better situational awareness. If effective cleanup technologies do not appear soon, then this kind of tracking will become more and more important.

6) Anything else we should watch out for in the near future?

There is some frustration in the field because the technical ideas often get ahead of the business model. Swiss researchers had planned to deploy CleanSpace One as a small debris-removal mission, but Swiss Space Systems went bankrupt, casting doubt on whether it would fly. That illustrates the broader problem: people are happy to pay to keep their satellites operating, but not necessarily to bring broken hardware back down. Over time, though, we are likely to see much more attention paid to graveyard orbits, deliberate deorbiting, and eventually legislation. At the very least, it would help enormously if countries stopped blowing up satellites to test anti-satellite weapons.

Zinger: TEDxMSVU and “Light Matters”